The present invention relates to the art of preparing bivalves recovered from a marine environment for human consumption without fear of contaminants resulting from polluted waters.
Bivalves, such as clams, oysters, mussels, etc., have hinged double shells that can be opened and closed by the bivalve which pumps or passes water through its system at various rates while absorbing oxygen from the water and trapping food, such as minute plankton and the like. In recent years, the growth in population around the coastal areas, where many bivalves are recovered for human consumption, has resulted in an increase in discharge of untreated domestic sewage and industrial waste into natural waters. This has rendered many of the otherwise useable beds of bivalves unmarketable because of the accumulation of undesirable microbiological agents, such as disease causing bacteria and viruses. This has been especially true as relates to certain types of hepatitis which has been transmitted through consumption of bivalves.
Consequently, suitable locations for harvesting bivalves for human consumption has been greatly diminished in recent years as a result of bacteriological examinations of the water near the harvesting area. That is, shellfish are not permitted to be taken from areas that contain predetermined bacteria counts or degrees of pollution. Such waters, are known as uncertified waters.
Due to the nature of the bivalve feeding system, however, oysters and clams from a polluted area have the capability of cleansing or depurating themselves when placed in clear waters, under the proper conditions. The rate of depuration varies with the type of bivalve and more specifically with the pumping rate of the particular bivalve. The pumping rate varies with the different conditions of the medium, but the water temperature has been known to be very important.
In the past, it has been suggested to treat tainted bivalves by submerging them in a tank of continuously moving ultraviolet ray treated salt water, the depth of which varies from 1/16th inch to 12 inches from 1 to 336 hours at water temperatures between 34.degree. and 90.degree. F. This system employs the use of a shallow tank from which water is pumped into a second smaller tank placed directly under ultraviolet lamps and then back into the first tank which holds the bivalves.
It has also been suggested in the past to wash the outsides of the shells and the like, by a chlorinated solution to disinfect the outside surfaces of the shells, and then to remove all traces of chlorine, prior to placing the shells in sterile water for self-purification. While these systems have proved satisfactory under certain conditions, and in particular under experimental or laboratory conditions, they have been less satisfactory on a large scale adapted for economic utilization of large harvesting areas located in polluted waters.
Another system disclosed in U.S. Pat. No. 3,641,982 to Woodridge, et al., is an open end system of continuously flowing water taken directly from the source from which the bivalves have been removed and back into the initial water source. This open end system includes a pump which pumps the water from the source through its radiation sterilizer, such as a gamma or nuclear radiation irradiator, or special industrial or commercial ultraviolet water purifiers, so that sterilized water is provided which is substantially similar to the waters from which the oysters have been removed. This water is fed into large tanks at several levels of the tank where oysters may be located on removable shelves. The tanks also have means other than the action produced by the entering water for producing movement of the water in the tank. The water leaves the tank from the bottom and passes through a second sterilizer essentially identical with the first sterilizer and back into the original water source.
As in other prior art systems, the strictly irradiation type of system incurs many problems basically because of the lack of control of the temperature of the water. In particular, this lack of temperature control is degrading to the texture of the bivalve, thus rendering the bivalve meat soft and inelastic. Furthermore, the continuous use of radiation to continuously purify a large volume of bivalves on a commercial scale consumes a great amount of energy. See, for example, U.S. Pat. No. 4,537,149 to Ryan.
It is an object, therefore, of the present invention, to provide an improved bivalve depuration system for preparation of bivalves on a commercial scale without the aforementioned drawbacks. Other benefits and advantages will be realized upon review of the present specification and claims.